1. Field of the Invention
The present invention relates to a radio wave absorbing coating composition and to a coated object that is obtained using this radio wave absorbing coating composition.
Priority is claimed on Japanese Patent Application No. 2005-188408, filed Jun. 28, 2005, the contents of which are incorporated herein by reference.
2. Description of Related Art
In recent years, high-speed information processing has been demanded in electronic instruments for personal digital assistants such as personal computers, mobile telephones, and digital cameras. In order to meet these demands, clock frequencies that operate a circuit has been increasing, and accordingly electromagnetic wave radiations are tend to be generated easily from circuit modules and transmission paths.
Moreover, there have also been demands for size reductions in electronic instruments for personal digital assistants, and higher circuit packaging densities have been sought in conjunction with these demands. As a result, signal interference that is caused by electromagnetic wave noise between circuits tends to be generated easily. Generation of this type of electromagnetic radio wave noise affects other instruments located around the electronic instruments for personal digital assistants, and there is also a possibility that normal usage of the electronic instruments for personal digital assistants themselves might be interrupted.
Accordingly, suppressing of electromagnetic wave radiation to outside from these instruments and suppressing of electromagnetic wave noise inside the instruments are significant problems in electronic instruments for personal digital assistants.
In Japanese Unexamined Patent Application, First Publication No. H10-7867, a description is given how the radio wave absorption properties are obtained in 1 to 18 GHz frequency band by employing a structure in which a bottom layer film is formed on an iron plate using a liquid composition that contains a nickel-zinc based spinel type ferrite sintered powder and a resin, and a top layer is formed thereon by coating a slurry composition that is obtained by kneading a cement mortar into a liquid composition that contains a graphite carbon ultrafine powder and a resin.
However, with a structure as described in Japanese Unexamined Patent Application, First Publication No. H10-7867, there has been insufficient absorption performance for radio waves in 40 MHz to 3 GHz frequency band which causes most of the problems in electromagnetic wave radiations to outside from electronic instruments for personal digital assistants, and in electromagnetic wave noise inside the electronic instruments for personal digital assistants.
The present invention was conceived in view of the above described circumstances and it is an objective thereof to provide a radio wave absorbing coating composition that provides an excellent absorption performance of radio waves in 40 MHz to 3 GHz frequency band and also a coated object that is formed by using the radio wave absorbing coating composition.